C.F. Martin Acoustic Guitar Martin Flexible Core FX 92/8 Phosphor Bronze .012 - .054, MFX-7404MartyLJuly 25, 2011I use these on my Epi AJ-500Re to help with playability. It's an attractive, solid, all-wood instrument, but the action was a little stiff. Since I've been using these, I use this particular guitar more often and find it easier on finger joints. They don't last as long as extended play strings, and seem to lose flexibility after a month or so. I also like FX strings for my 12 string for the same reason.